Phosphoenolpyruvate Carboxykinase in Plants Exhibiting Crassulacean Acid Metabolism

Dittrich, P.; Campbell, Wilbur H.; Black, Clanton C.

doi:10.1104/pp.52.4.357

Cited by 142 publications

(64 citation statements)

References 26 publications

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“…Like RuBPc the activity of these C4 enzymes on a Chl basis, was greatest in the ME, probably because the Chl content was so low in this layer, but unlike RuBPc their activity was lowest in the PM, not the SM. The rates of all the enzymes measured were within the range of other studies on CAM plants (7,13).…”

Section: Resultssupporting

confidence: 59%

Carbon Flow and Metabolic Specialization in the Tissue Layers of the Crassulacean Acid Metabolism Plant, Peperomia camptotricha

Nishio

Ting²

1987

Plant Physiol.

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Leaves of Peperomia camptotricha contain three distinct upper tissue layers and a one-cell thick lower epidermis. Light and dark CO2 fixation rates and the activity of ribulose bisphosphate carboxylase/oxygenase and several C4 enzymes were determined in the three distinct tissue layers. The majority of the C4 enzyme activity and dark CO2 fixation was associated with the spongy mesophyll, including the lower epidermis; and the least activity was found in the median palisade mesophyli. In contrast, the majority of the C3 activity, that is ribulose bisphosphate carboxylase/ oxygenase and light CO2 fixation, was located in the palisade mesophylU. In addition, the diurnal flux in titratable acidity was greatest in the spongy mesophyll and lowest in the palisade mesophyll. The spatial separation of the C3 and C. phases of carbon frixation in P. camptotricha suggests that this Crassulacean acid metabolism plant may have low photorespiratory rates when it exhibits daytime gas exchange (that is, when it is well watered). The results also indicate that this plant may be on an evolutionary path between a true Crassulacean acid metabolism plant and a true C4 plant.CAM plants usually exhibit a temporal separation of the C3 and C4 phases of carbon fixation. The initial CO2 fixation produces malic acid by the C4 phase at night, when the stomata are open, and subsequent decarboxylation of the C4 products and refixation ofthe released CO2 via the C3 phase (reductive pentose phosphate pathway) occurs during the day, when stomata are closed. In contrast, C4 plants are characterized by a physical separation ofthe C3 and C4 phases ofcarbon fixation into bundle sheath cells and mesophyll cells, respectively. The malic acid or other C4 acid produced in the mesophyll cells is transported to the bundle sheath cells, where it is decarboxylated and the released CO2 refixed via the C3 phase.

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Section: Resultssupporting

confidence: 59%

Carbon Flow and Metabolic Specialization in the Tissue Layers of the Crassulacean Acid Metabolism Plant, Peperomia camptotricha

Nishio

Ting²

1987

Plant Physiol.

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“…In addition, PEP carboxylase has little or no activity at pH 6, whereas PEP carboxykinase at this pH has considerable activity (7,9), with the optimum pH ranging between 6.4 and 6.7 (20).…”

Section: Methodsmentioning

confidence: 99%

“…All enzymatic activities are expressed on a per-gram-freshweight basis, because the high concentration of phenolic substances in grapes (28) causes serious interference with the common methods of protein determination (21 (3,7,9,22). In addition, PEP carboxylase has little or no activity at pH 6, whereas PEP carboxykinase at this pH has considerable activity (7,9), with the optimum pH ranging between 6.4 and 6.7 (20).…”

Section: Methodsmentioning

confidence: 99%

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Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

Ruffner

Kliewer²

1975

Plant Physiol.

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Phosphoenolpyruvate (PEP) carboxykinase activity was found in crude extracts of 'Pinot noir' grape berries. The enzyme required ATP, Mn'+ plus Mg, a pH of 6.6, and a temperature of 40 C for maximum activity. The range in concentration of oxaloacetic acid needed for maximum phosphoenolpyruvate carboxykinase activity was 5 to 10 mM, and the Km for HC03-in the exchange of 1CO2 into oxaloacetic acid was 26.8 mM.Changes in the activity of PEP carboxykinase and PEP carboxylase in berries were studied at weekly intervals throughout fruit development. PEP carboxykinase had maximum activity 4 weeks after flowering, and during the following 11 weeks remained relatively constant. The activity of PEP carboxylase was 2-to 4-fold higher than PEP carboxykinase throughout fruit development, and changed little except for a sharp reduction at the onset of ripening.

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“…by CAM plants. In specific C 4 plants three 4-carbon acid decarboxylases were found and similarly we found NADP + -or NAD + -dependent malic enzyme or PEP carboxykinase in specific CAM plants (Hatch et al 1970;Dittrich et al 1973;Dittrich 1975). The crucial enzyme to recover pyruvate carbon during the day and to form PEP for daily carbohydrate storage, pyruvate Pi-dikinase, was quickly found (Kluge and Osmond 1971;Sugiyama and Laetsch 1975).…”

Section: The Daily Cam Carbohydrate Cyclementioning

confidence: 83%

Crassulacean acid metabolism photosynthesis: ‘working the night shift’

Black

Osmond

Discoveries in Photosynthesis

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Crassulacean acid metabolism (CAM) can be traced from Roman times through persons who noted a morning acid taste of some common house plants. From India in 1815, Benjamin-Heyne described a 'daily acid taste cycle' with some succulent garden plants. Recent work has shown that the nocturnally formed acid is decarboxylated during the day to become the CO 2 for photosynthesis. Thus, CAM photosynthesis extends over a 24-hour day using several daily interlocking cycles. To understand CAM photosynthesis, several landmark discoveries were made at the following times: daily reciprocal acid and carbohydrate cycles were found during 1870 to 1887; their precise identification, as malic acid and starch, and accurate quantification occurred from 1940 to 1954; diffusive gas resistance methods were introduced in the early 1960s that led to understanding the powerful stomatal control of daily gas exchanges; C 4 photosynthesis in two different types of cells was discovered from 1965 to ∼1974 and the resultant information was used to elucidate the day and night portions of CAM photosynthesis in one cell; and exceptionally high internal green tissue CO 2 levels, 0.2 to 2.5%, upon the daytime decarboxylation of malic acid, were discovered in 1979. These discoveries then were combined with related information from C 3 and C 4 photosynthesis, carbon biochemistry, cellular anatomy, and ecological physiology. Therefore by ∼1980, CAM photosynthesis finally was rigorously outlined. In a nutshell, 24-hour CAM occurs by phosphoenol pyruvate (PEP) carboxylase fixing CO 2 (HCO 3 − ) over the night to form malic acid that is stored in plant cell vacuoles. While stomata are tightly closed the following day, malic acid is decarboxylated releasing CO 2 for C 3 photosynthesis via ribulose bisphosphate carboxylase oxygenase (Rubisco). The CO 2 acceptor, PEP, is formed via glycolysis at night from starch or other stored carbohydrates and after decarboxylation the three carbons are restored each day. In mid to late afternoon the stomata can open and mostly C 3 photosynthesis occurs until darkness. CAM photosynthesis can be both inducible and constitutive and is known in 33 families with an estimated 15 to 20 000 species. CAM plants express the most plastic and tenacious photosynthesis known in that they can switch photosynthesis pathways and they can live and conduct photosynthesis for years even in the virtual absence of external H 2 O and CO 2 , i.e., CAM tenaciously protects its photosynthesis from both H 2 O and CO 2 stresses.Abbreviations: CAM -Crassulacean acid metabolism; PEP -phosphoenol-pyruvate; Rubisco -ribulose 1,5-bisphosphate carboxylase oxygenase; C 3 -three carbon photosynthesis; C 4 -four carbon photosynthesis; PEPCase -phosphoenol pyruvate carboxylase 330

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Phosphoenolpyruvate Carboxykinase in Plants Exhibiting Crassulacean Acid Metabolism

Abstract: Phosphoenolpyruvate carboxykinase has been found in significant activities in a number of plants exhibiting Crassulacean

Cited by 142 publications

References 26 publications

Carbon Flow and Metabolic Specialization in the Tissue Layers of the Crassulacean Acid Metabolism Plant, Peperomia camptotricha

Carbon Flow and Metabolic Specialization in the Tissue Layers of the Crassulacean Acid Metabolism Plant, Peperomia camptotricha

Phosphoenolpyruvate Carboxykinase Activity in Grape Berries

Crassulacean acid metabolism photosynthesis: ‘working the night shift’

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